The present invention relates to an optical tomographic imaging system for acquiring a tomographic image of an object under measurement and more specifically to an optical tomographic imaging system comprising an optical probe rotatably holding an optical fiber that guides measuring light to the object under measurement and guides returning light from the object under measurement to acquire an optical tomographic image of the object under measurement, whereby the extra length of the optical probe can be handled according to a length up to the object under measurement at a location to be examined in such a manner as to permit adjustment of the use length of the optical probe according to the length to the object under measurement.
Acquisition of a cross-sectional image of a sample under measurement such as biological tissue without cutting thereinto may be achieved using an optical tomographic imaging system known in the art employing optical coherence tomography (OCT) measuring.
The OCT measuring is a kind of optical interferometric measurement using optical interference that occurs only when the optical path lengths of the measuring light and the reference light, into which the light from the light source is divided, are matched to within the coherence length of the light from the light source.
An optical tomographic imaging system using the OCT measuring is disclosed, for example, in JP 2006-215005 A filed by one of the Applicants of the present application, comprising a light source; optical splitting means for splitting the light emitted from the light source into measuring light and reference light; a probe including a measuring unit for irradiating the object under measurement with the measuring light and detecting the reflected light, an optical fiber for transmitting the measuring light and the reflected light, and a transparent tube covering the optical fiber and the measuring unit; optical path length changing means for changing the optical path length of the reference light to a length that is a sum of the optical path lengths of the measuring light and the reflected light; combining means for combining the reference light having its optical path length changed and the reflected light; and interference light detecting means for detecting interference light produced from the combined reference light and reflected light to generate a tomographic image from the detected interference light. With the optical tomographic imaging system disclosed in JP 2006-215005 A, the measuring unit located close to the tip of the probe is introduced to a position to be measured and rotated by turning the optical fiber to acquire tomographic images at a plurality of points on the object under measurement at a location to be measured as the measuring unit rotates, thus reconstructing a two-dimensional sectional image.
The optical path length changing means disclosed in JP 2006-215005 A comprises a first optical path length changing means for changing the optical path length of the reference light according to the sum of the optical path lengths of the measuring light and the reflected light that varies as the measuring position in the object under measurement in a depthwise direction is changed and a second optical path length changing means for changing the optical path length of the reference light to correct a manufacturing error made in the length of the probe that is attached to the main body of the system. Thus, in cases where two or more probes are used by replacing one with another depending upon the length required, when variations arise in the optical path lengths of the measuring light and the reflected light due to variations attributable to manufacturing errors in the lengths of the individual probes, the optical tomographic imaging system disclosed in JP 2006-215005 is capable of adjusting the optical path length of the reference light according to such variations using the second optical path length changing means and thus capable of preventing variation in the measuring range that might otherwise be caused by variation in length among the probes used. In particular, the system disclosed in JP 2006-215005 A is capable of accurately matching the measureable region with a set measuring region by preventing variation in the measuring range caused by variation in length among the probes with the two optical path length changing means.